FIX: Symmetric key encryption takes longer time in SQL Server 2017 than in SQL Server 2012

Assume that you use Symmetric key to encrypt data in a table in Microsoft SQL Server 2017. In this scenario, you may notice that the symmetric key encryption in SQL Server 2017 takes longer to run when compared to Microsoft SQL Server 2012.

This issue is fixed in the following cumulative update for SQL Server:

Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:

In SQL Server 2012, the operating system calls to the data encryption API executed in non-preemptive mode. If these calls take a significant amount of time, SQL Server could enter a non-yielding condition and generate a dump. 

After SQL Server 2012, a change was made to switch to preemptive mode for every such encryption API call. This addresses the scheduling stability issue, but also increases time required to switch to preemptive mode and back again. For workloads in which an encryption API is called frequently, the overall performance effect may be substantial. This change introduces a new trace flag (TF) 4640 that reverts to SQL 2012 behavior.